The present claimed invention relates to the field of display device technology. More particularly, the present claimed invention relates to a display device formation method and apparatus for reducing ambient light penetration into a display device.
Liquid crystal display devices (LCDs) are well known in the art. In particular, microdisplays are the finest panel displays which offer low power, high resolution and greater functional integration. Common to many microdisplay concepts is the use of CMOS (complementary metal oxide silicon) backplane upon which a light modulating layer is placed. Typically in microdisplays, the topmost level fabricated on the bottom substrate (sometimes referred to as the xe2x80x9cbackplanexe2x80x9d) is an array of metal pixels which are coupled to underlying transistors. A layer of liquid crystal material is disposed over the metal pixels. By selectively controlling the underlying transistors, an electric field can be generated at the array of metal pixels. This electric field, in turn, causes the liquid crystal material to selectively allow for the transmission of light therethrough. In so doing, the display is controlled to produce an image. For a microdisplay based on liquid crystal on silicon (LCOS) technology, the backplane is subjected to strong incident light in order to project a produced image onto a focal plane.
Unfortunately, subjecting a LCOS microdisplay to strong incident light can have deleterious consequences. Specifically, such strong incident light poses a potential threat to device operation due to photoelectron generation and interference. That is, in some conventional displays incident light can penetrate through the upper portion of the backplane and affect the operation of underlying active devices.
As yet another drawback to some conventional microdisplay devices, a thin passivation layer is required on top of the metal pixel to achieve optimal reflectance and a reduced voltage drop across the passivation layer.
In addition, excessive step height differences between pixels can occur. Such step height differences are caused, for example, by a need to overetch the metal layer comprising the array of metal pixels. Such excessive step height coupled with a thin passivation layer can result in poor sidewall coverage and may ultimately compromise passivation integrity. In all LC devices, the LC optic axis needs to be uniformly aligned to deliver desired optical performance. This is usually accomplished with an oriented alignment layer (e.g. polyimide) that aligns LC after fill. Excessive gouging between the pixel cases difficulty during the LC alignment process due to nonuniformity of the spin coated polyimide.
Thus, a need exists for a display device formation method and apparatus which reduces the penetration of incident ambient light into the backplane. Still another need exists for a display device formation method and apparatus which meets the above need and reduces the excessive step height between pixels thus reducing liquid crystal alignment difficulty and improving passivation integrity.
The present invention provides a display device formation method and apparatus which reduces the penetration of incident ambient light into the backplane. The present invention further provides a display device formation method and apparatus which achieves the above accomplishment and reduces the excessive step height between pixels thus reducing liquid crystal alignment difficulty and improving passivation integrity.
In one embodiment, the present invention recites forming a plurality of metal pixels wherein adjacent ones of the plurality of metal pixels have a gap region disposed therebetween. The present embodiment then recites depositing a light absorbing antireflective coating (ARC) material within the gap region to form a light shield such that transmission of incident light through the gap region towards underlying active devices is reduced. Next, the present embodiment deposits a passivation layer above the plurality of metal pixels and the ARC material to passivate the backplane. As a result, the ARC material disposed in the gap region reduces the transmission of incident light between the metal pixels and towards the active devices of the display.
In yet another embodiment, the present invention includes the steps of the above-described embodiment and further comprises depositing a layer of liner material prior to depositing a conductive layer of antireflective coating material.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.